One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,4)(6,8)(9,10)(11,20)(12,24)(13,28)(14,19)(15,18)(16,22)(17,26)(21,37)(23,33)(25,40)(27,36)(29,32)(30,35)(31,39)(34,38) involution — undirected(9,11,13,22,15,23,14,29)(10,16,19,20,18,32,28,33)(12,25,26,21,27,38,30,39)(17,34,24,37,35,40,36,31)(2,4)(9,12,13,26,15,27,14,30)(10,17,19,24,18,35,28,36)(11,21,22,38,23,39,29,25)(16,31,20,34,32,37,33,40)(5,6,7,8)(10,18)(16,32)(17,35)(19,28)(20,33)(24,36)(31,37)(34,40)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.